1. Field of the Invention
This invention relates to a silver catalyst for the production of ethylene oxide, a method for the manufacture of the catalyst, and a method for the production of ethylene oxide, and more particularly to a silver catalyst excelling in catalytic performance and allowing production of ethylene oxide with a high selectivity for a long time, a method for the production of ethylene oxide by the use of the silver catalyst, and a completely satisfying method for the manufacture of the silver catalyst.
2. Description of the Related Art
The production of ethylene oxide by the catalytic gas phase oxidation of ethylene with molecular oxygen in the presence of a silver catalyst has been widely practiced on the commercial scale. As concerns the silver catalyst to be used for the catalytic gas phase oxidation, numerous inventions covering carriers for the catalyst, methods for deposition of the catalyst on a carrier, reaction accelerators for the catalysis, etc. have been filed for patents.
For example, the silver catalyst formed by depositing silver and at least one promoter selected from the group consisting of alkali metals and alkali metal compounds on a porous carrier of a specific shape (U.S. Pat. No. 4,645,754, U.S. Pat. No. 4,769,358, etc.) and the silver catalyst formed by depositing silver and cesium on an .alpha.-alumina carrier having the surface thereof coated with amorphous silica or amorphous silic.alpha.-alumina (U.S. Pat. No. 5,077,256, U.S. Pat. No. 5,395,812, etc.) have been known.
Notwithstanding these silver catalysts have the selectivity thereof already exalted to high levels, the fact that their selectivity are still desired to be further improved is logically explained by appreciating the scale of production of ethylene oxide which is so large that the increase of only 1% in the selectivity brings an extremely high economic effect of allowing a notable saving of the raw material ethylene. By the same token, the improvement of the silver catalyst in service life and in durability brings an enormous economic effect.
In the circumstances, the development of a silver catalyst which is further improved in such catalytic qualities as activity, selectivity, and service life has been a constant theme to be pursued by researchers in the pertinent technological field.
An object of this invention, therefore, is to provide a silver catalyst which excels in catalytic performance and permits production of ethylene oxide with a high selectivity for a long time, a method for the production of ethylene oxide by the use of the silver catalyst, and a method for completely satisfactory manufacture of this silver catalyst.